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biochem > nitrogen metabolism > Flashcards

nitrogen metabolism Flashcards

1
Q

primary metabolites

A

needed for normal operation of metabolic pathways; amino acids, nucleotides, RNA, DNA, B vitamins

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2
Q

secondary metabolites

A

those organic compounds not needed for cell growth, development, or reproduction

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3
Q

alkaloids

A

plant-derived nitrogen-containing secondary metabolites; caffeine, morphine, taxol, LSD

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4
Q

fungal metabolites

A

penicillin, streptomycin, cyclosporin

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5
Q

nutritionally essential amino acids

A

PVT TIM HiLL ( phenylalanine, valine, tryptophan, threonine, isoleucine, methionine, histidine, leucine, lysine)

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6
Q

conditionally essential amino acids

A

arginine, tyrosine, cysteine

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7
Q

Arginine

A

humans make arginine, but more is needed for unimpaired growth during childhood and pregnancy

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8
Q

tyrosine

A

becomes essential, whenver Phe is inadequate

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9
Q

cysteine

A

becomes essential, whenever Met is inadequate

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10
Q

why must diet be varied?

A

to get an adequate balance of AAs

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11
Q

what is low in essential amino acids?

A

vegetables and even animal proteins

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12
Q

how do omnivores gain advantage?

A

by eating both plant and animal protein

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13
Q

what are the sources of amino acids?

A

intracellular proteolysis, digestion of proteins in foodstuffs, de novo AA synthesis

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14
Q

intracellular proteolysis

A

removes misfolded as well as old and damaged proteins, supplies essential AAs when dietary intake is insufficient, controls cell-cycle transitions and cell disjunction

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15
Q

digestion of proteins in foodstuffs

A

supplies both nutritionally essential and nutritionally nonessential AAs

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16
Q

de novo AA synthesis

A

provides nutritionally nonessential AAs that are needed for protein synthesis; adjusts amino acid pools in different tissues, adjusts energy metabolism by controlling concentrations of central pathway metabolites; allows cells to adapt to metabolic stress; needed to make nucleotides, heme, hormones, as well as neurotransmitters

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17
Q

Intracellular protein turnover

A

turnover rate depends on metabolic state; greater protein degradation occurs whenever nitrogen intake is low because cells need essential amino acids to make vitally needed proteins

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18
Q

what are the three pathways for intracellular protein turnover?

A

lysosome pathway, proteasome pathway, autophagic pathway

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19
Q

lysosome pathway

A

lysosome is an acidic compartment where proteins are protonated and undergo partial unfolding due to repulsion, making them more susceptible to proteolysis

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20
Q

proteasome pathway

A

ubiquitin is a 8.6-kDa protein that is enzymatically joined to unfolded proteins, marking them for breakdown. only ubiquitinated proteins can enter proteasomes, barrel-like macromolecular structures that use on-board proteases to form small peptides and AAs

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21
Q

autophagic pathway

A

uses ubiquitin system and lysosomes to remove old organelles that are first engulfed in an autophagic vacuole

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22
Q

proteolysis

A

enzymatic cleavage of proteins

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23
Q

saliva (proteins)

A

low levels of proteases

24
Q

stomach: low pH (proteins)

A

pepsin

25
Q

small intestine; neutral pH (protein fragments)

A

fragments can’t refold at neutral pH; chymotrypsin, trypsin, carboxypeptidase, elastase

26
Q

after getting through the proteins and protein fragments what are we left with?

A

mainly amino acids and di- and tri- peptides

27
Q

zymogen activation

A

zymogen-> proteolytic cleavage-> active enzyme; inactive enzymes are safer to store; prevents autophagy and apoptosis

28
Q

what are the 4 major digestive proteases?

A

pepsinogen, chymotrypsinogen, trypsinogen, procarboxypeptidase

29
Q

pepsinogen

A

active enzyme=pepsin, optimally active at pH 1-3

30
Q

chymotrypsinogen

A

active enzyme=chymotrypsin, optimally active at pH 7

31
Q

trypsinogen

A

active enzyme: trypsin, optimally active at pH 7

32
Q

procarboxypeptidase

A

active enzyme: carboxypeptidase, optimally active at pH 7

33
Q

autocatalysis

A

any process in which a reaction product is capable of catalyzing its own formation

34
Q

pepsinogen is formed in and released by ____________ cells, which store pepsinogen in ___________

A

gastric chief cells; secretory granules

35
Q

once a few pepsin molecules are formed by acid catalysis…

A

they rapidly cleave many pepsinogen molecules, each forming considerably more molecules of catalytically active pepsin

36
Q

what mediate catalysis at low pH for pepsin?

A

two active-site aspartyl residues

37
Q

chymosin

A

acid protease that curds milk to hasten pepsin cleavage

38
Q

what is NOT absorbed by healthy intestine?

A

dietary proteins; foreign proteins are immunogenic; must be proteolyzed to amino acids, di- &tri-peptides

39
Q

proteolysis of protein foodstuffs process begins by making what?

A

zymogens; synthesized and stored in pancreas; secreted into small intestine-> only then converted to active catalysts

40
Q

trysinogen activation

A

pancreas makes & stores trypsinogen in vesicles; secretory vesicles contain trysin inhibitor; prevents unwanted proteolysis of host cells; enterokinase converts trysinogen into trypsin; trypsin activates chymotrypsinogen to chymotrypsin

41
Q

enterokinase

A

an ectoprotease on intestinal mucosal wall

42
Q

pro-carboxypeptidase

A

activated to carboxypeptidase in a cleavage reaction that is catalyzed by trypsin

43
Q

AAs and small peptides are…

A

actively transported (against the concentration gradient) into intenstinal brush border cells

44
Q

amino acids and sodium ions are transported in the same direction, and transport is driven by…

A

transmembrane ion gradient (high na+ in intestinal lumen & low na+ in brush border)

45
Q

cells use _____________ to drive Na+ outward and K+ inward

A

ATP-hydrolysis dependent pumps

46
Q

what drives AA uptake?

A

cell’s chemiosmotic gradient

47
Q

organs selectively import AAs they need thru…

A

organ-specific expression of AA-selective transporters

48
Q

true nitrogen balance

A

intake=excretion

49
Q

positive nitrogen balance

A

intake>excretion

50
Q

negative nitrogen balance

A

intake<excretion

51
Q

positive nitrogen balance is required for…

A

growth in childhood, growth in pregnancy, healing of wounds, convalescence

52
Q

negative nitrogen balance occurs during…

A

starvation, malnutrition, disease (burns, trauma, surgery)

53
Q

marasmus

A

malnutrition associated with extensive tissue and muscle wasting, with little/no edema
features: loose folds of skin hanging over buttocks
severe deficiency of nearly all nutrients, especially protein, carbohydrates, and lipids

54
Q

protein-energy malfunction

A

resulting from inadequate intake of protein and calories

55
Q

Kwashiorkor

A

translation: sickness last baby gets when the new baby arrives
acute childhood protein malnutrition
inadequate protein intake but adequate caloric intake

56
Q

characteristics of kwashiorkor

A

irritability (neurotransmitter deficit), big belly (liver enlarged with fatty infiltrates) kids are always hungry & eat too much cassava (excess carbohydrate is stored as fat in liver), edema hypoalbuminemia causes osmotic imbalance within ankles, feet, and belly

biochem (37 decks)

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